On 6/19/2024 4:29 PM, Udit Kumar wrote:

As per Errata i2310[0], Erroneous timeout can be triggered, if this Erroneous interrupt is not cleared then it may leads to storm of interrupts, therefore apply Errata i2310 solution.

[0] https://www.ti.com/lit/pdf/sprz536 page 23

Fixes: b67e830d38fa ("serial: 8250: 8250_omap: Fix possible interrupt storm on K3 SoCs") Cc: stable@vger.kernel.org Signed-off-by: Udit Kumar u-kumar1@ti.com

---

Change logs Changes in v3:

• CC stable in commit message

Link to v2: https://lore.kernel.org/all/20240617052253.2188140-1-u-kumar1@ti.com/

Changes in v2:

• Added Fixes Tag and typo correction in commit message
• Corrected bit position to UART_OMAP_EFR2_TIMEOUT_BEHAVE

Link to v1 https://lore.kernel.org/all/20240614061314.290840-1-u-kumar1@ti.com/

drivers/tty/serial/8250/8250_omap.c | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c index 170639d12b2a..ddac0a13cf84 100644 --- a/drivers/tty/serial/8250/8250_omap.c +++ b/drivers/tty/serial/8250/8250_omap.c @@ -115,6 +115,10 @@ /* RX FIFO occupancy indicator */ #define UART_OMAP_RX_LVL 0x19 +/* Timeout low and High */ +#define UART_OMAP_TO_L 0x26 +#define UART_OMAP_TO_H 0x27

/*

• Copy of the genpd flags for the console.
• Only used if console suspend is disabled

@@ -663,13 +667,24 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id) /* * On K3 SoCs, it is observed that RX TIMEOUT is signalled after

• * FIFO has been drained, in which case a dummy read of RX FIFO
  

• * is required to clear RX TIMEOUT condition.
  

• * FIFO has been drained or erroneously.
  

• * So apply solution of Errata i2310 as mentioned in
  

• * https://www.ti.com/lit/pdf/sprz536
  

  */ if (priv->habit & UART_RX_TIMEOUT_QUIRK &&

•    (iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT &&
  

•    serial_port_in(port, UART_OMAP_RX_LVL) == 0) {
  

• serial_port_in(port, UART_RX);
  

• (iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT) {
  

This still doesn't match the errata workaround described in the above doc. Need a check for RX FIFO LVL to be empty (like before). Else we end up applying workaround on every timeout (including those that are not spurious) which is undesirable in the IRQ hotpath.

• unsigned char efr2, timeout_h, timeout_l;
  

• efr2 = serial_in(up, UART_OMAP_EFR2);
  

• timeout_h = serial_in(up, UART_OMAP_TO_H);
  

• timeout_l = serial_in(up, UART_OMAP_TO_L);
  

• serial_out(up, UART_OMAP_TO_H, 0xFF);
  

• serial_out(up, UART_OMAP_TO_L, 0xFF);
  

• serial_out(up, UART_OMAP_EFR2, UART_OMAP_EFR2_TIMEOUT_BEHAVE);
  

• serial_in(up, UART_IIR);
  

• serial_out(up, UART_OMAP_EFR2, efr2);
  

• serial_out(up, UART_OMAP_TO_H, timeout_h);
  

• serial_out(up, UART_OMAP_TO_L, timeout_l);
  

  }

/* Stop processing interrupts on input overrun */